Al Doping Research Articles

Visible Light-Driven Photocatalysis of Al-Doped SrTiO3: Experimental and DFT Study

Environmental problems associated with water pollution caused by organic dyes have raised serious concerns. In this context, photocatalytic processes have proven to be promising and environmentally friendly methods for water purification utilising abundant solar energy. In this study, a SrTiO3-based photocatalyst was modified by doping with Al ions and the deposition of dual co-catalysts (Rh/Cr2O3 and CoOOH) to enhance the photocatalytic decomposition efficiency of methylene blue (MB). Pure perovskite SrTiO3 was synthesised by chemical precipitation followed by calcination at 1100 °C. Al-doped SrTiO3 with deposited co-catalysts showed 3.2 times higher photocatalytic activity compared to unalloyed SrTiO3 with co-catalysts in MB decomposition under visible radiation. This study highlights the effectiveness of using dual co-catalysts and low-valence metal doping to enhance the efficiency of the photocatalytic decomposition of organic pollutants. The density functional theory analysis results show that the Al doping of SrTiO3 improves charge separation and increases the lifetime of photogenerated electrons and holes while maintaining the size of the forbidden band, which confirms its effectiveness for enhancing photocatalytic activity.

Reinforcing Photogenerated Carrier Extraction of Environment-Friendly InP/ZnSeS Quantum Dots for High-Performing Photoelectrochemical Photodetection and Solar Energy Conversion.

Colloidal InP/ZnSeS-based quantum dots (QDs) are considered promising building blocks for light-emitting devices due to their environmental friendliness, high quantum yield (QY), and narrow emission. However, the intrinsic type-I band structure severely hinders potential photoelectrochemical (PEC) applications requiring efficient photoexcited carrier separation and transfer. In this study, the optoelectronic properties of InP/ZnSeS QDs are tailored by introducing Al dopants in the ZnSeS layer, which concurrently passivate the surface defects and act as shallow donor states for suppressed non-radiative recombination and improved charge extraction efficiency. Consequently, as-fabricated InP/ZnSeS:Al QDs-based PEC-type photodetector exhibited a high detectivity up to 1011 Jones and a remarkable responsivity of 0.66 AW-1 at 600nm even under self-powered condition (0V bias). In addition, as-prepared InP/ZnSeS:Al QDs-based photoanode can be alternatively used for PEC hydrogen generation, showing an H2 production rate of 73.7µmol cm-2h-1 under 1 sun illumination (AM 1.5G, 100mW cm-2). The results offer a prospective strategy for optimizing eco-friendly QDs for high-performance multifunctional light detection/conversion devices.

Effects of Al doping on structural, optical, morphological, and low-concentration CO2 gas sensing properties of ZnO nanoparticles synthesized by sol-gel method

Abstract This work examines the morphological, structural, optical, and gas-sensing characteristics of ZnO thin films doped with Al that were created by the sol-gel spin coating technique. The thin films, doped with varying aluminum concentrations (0%, 2%, and 5%), were characterized using XRD, UV-visible spectroscopy, and FE-SEM to assess their crystallinity, band gap, and surface morphology. XRD analysis confirmed the incorporation of Al into the ZnO lattice without forming secondary phases, while UV-visible spectroscopy revealed an increase in transmittance and band gap with higher Al doping. FE-SEM images showed a transition from agglomerated grains to smoother surfaces with increased Al content. Gas sensing performance was evaluated using low-concentration CO2 as the target gas. The results demonstrated that Al doping significantly enhances the CO2 sensing response, with the 5% Al-doped ZnO exhibiting the optimal sensitivity due to increased carrier concentration and improved surface interaction. These findings suggest that Al-doped ZnO thin films are promising candidates for efficient CO2 gas sensors, combining enhanced structural and optical properties with superior gas sensing capabilities.

Modulating Built‐In Electronic Configuration via Variable Al Doping for Robust Oxygen Evolution Reaction

Transition metal‐based electrocatalysts play a crucial role in the oxygen evolution reaction (OER). However, their heavy reliance on free electrons at the <i>d</i>‐band significantly limits the screening of potentially efficient, earth‐abundant alternatives. Despite extensive exploration of catalyst engineering through multi‐metal cooperation to modulate electron configuration by introducing additional transition metals, practical success remains elusive. Here, we present a straightforward electrodeposition method for preparing amorphous FeCoAl hydroxide catalysts. The introduction of Al contributes external free electrons, enabling a well‐defined electron configuration for intermediate adsorption. Al doping also adjusts the <i>d</i>‐band position of adjacent Co atoms, bringing them closer to the Fermi level and significantly enhancing intrinsic activity at the active sites. Furthermore, Al dopants facilitate rapid mass and charge transfer near the catalyst layer, promoting faster reaction kinetics. Leveraging these properties, the FeCoAl hydroxide catalyst achieves a large current density of 100 mA cm <sup>‐2</sup> at an overpotential of 340 mV, with a small Tafel slope of 29.1 mV dec <sup>‐1</sup>. Our work provides valuable insights for designing efficient electrocatalysts by leveraging free electron‐rich metal doping and expanding the parameter space for catalyst engineering.

Effect of Al-, In-, and Mg-doping in the ZnO on the structural, electrical, and optical properties of ZnO/CH3NH3PbI3 heterostructure

The creation of ZnO/CH3NH3PbI3 heterostructures with Aluminum (Al), Magnesium (Mg), and Indium (In) doped ZnO serving as an electron transport layer is the aim of this work. A favorable orientation for the CH3NH3PbI3 absorber layer crystallizes in the tetragonal phase [220], while ZnO crystallizes in the hexagonal phase [100]. This information is yielded by x-ray diffraction analysis. Al, In, and Mg doping of the transport layer has a significant effect on the optical characteristics like absorption and extinction coefficients, optical gaps, and optical and electrical conductivity. The UV-visible characterization of the heterostructures reveals that n-type doping can raise ZnO gap energy from 3.15 to 3.42 eV. The band gap energy of CH3NH3PbI3 is around 1.53-1.55 eV. Additionally, the absorption coefficient of each sample is high, it exceeds 105 cm-1. The ZnO thin films, both undoped and doped (with Al, In and Mg) exhibit an increase in refractive index from 1.97 to 2.13. The best dopant is found to be In. The refractive index of films composed of CH3NH3PbI3 is 3.13.

The enhancement in microstructure, optical and electromagnetic shielding properties of Al-doped Ag thin films by annealing treatment

Ag thin films having attractive optical transmittance and effective shielding capability are usually used as a preferred choice for the transparent electromagnetic shielding windows. Whereas, the Ag films are grown primarily via an island growth (Volmer-Weber) mechanism, which greatly restricts its application. In this study, by introducing Al atoms and suitable annealing treatment, the continuous and smooth Ag thin films are successfully fabricated by magnetron co-sputtering method. The effect of annealing temperature on the microstructure, optical and electromagnetic shielding properties of the films are conducted the comprehensive and profound study. Our results indicate that the 5 mol% Al-Ag thin film annealed at 200 °C could transform into planar growth structure, and display excellent the highest optical transmittance 89.15% at 550 nm. Meanwhile, the shielding effectiveness (SE) reaches a peak value of 28.1 dB. 500°C is estimated as the threshold annealing temperature of Al-Ag thin film with comprehensive performances gradually declining. Moreover, the Al dopants significantly improve the thermal stability of Ag thin films than that of the pure Ag films. These findings are of important guidance for the preparation of high-quality Al-Ag thin films to meet the practical applications.

Efficient photocatalytic degradation of methylene blue via synergistic dual co-catalyst on SrTiO3@Al under visible light: Experimental and DFT study

BackgroundPhotocatalytic oxidation is a green method for water purification. However, the operation of traditional photocatalysts depends on exposure to UV radiation, which only forms a small portion of the spectrum comprising sunlight. The expansion of photocatalyst absorption to the visible range of light could greatly improve the efficiency and economic viability of the process. MethodsThe photocatalyst was prepared by first synthesising SrTiO3 nanoparticles by chemical precipitation followed by calcination. Then, SrTiO3 was doped with aluminium using a flux method with Al2O3 and SrCl2 at 1150 °C. Finally, the dual co-catalysts, Rh/Cr2O3 and CoOOH, were photodeposited onto SrTiO3@Al via sequential irradiation. Significant findingsThe Rh/Cr2O3/SrTiO3@Al/CoOOH nanocomposite degraded 87% of methylene blue (MB) (10 mg/L) under visible light in 1 h, a 3.3-fold improvement over pure SrTiO3 and 2.1-fold over a similar commercial composite. This enhancement is due to efficient charge separation resulting from Al doping and improved carrier transport as a result of the anisotropic deposition of the co-catalysts. Optimisation showed that 20 mg of photocatalyst in 50 mL of MB solution (5 mg/L) degraded 100% thereof within 45 min. DFT calculations showed uneven electron distribution in SrTiO3′s conduction band and structural changes with Al doping, further enhancing photocatalytic activity.

Visible Light Driven Defect Mediated Photocatalytic Activity of Spray Pyrolyzed Ga and Al Doped ZnO Thin Film Electrodes

AbstractGa and Al doped ZnO thin film electrodes are spray deposited and explored for photocatalytic deterioration of methylene blue dye. X‐ray diffraction unveils both films to have highly textured growth along the (002) plane. The surface morphology is found to have near spherical and distorted rectangular particles for Ga and Al dopants, respectively. Photoluminescence emission study reveals that both films have visible light emissions in the violet, blue, and green regions due to oxygen vacancy defects. The deposited films exhibit a reasonably higher transmittance of 89 and 77 % with mobility of 30.5 and 29.6 cm2/Vs for Ga and Al doped ZnO, respectively. Cyclic test and photo‐corrosion studies performed for selected samples were indicating significant stability. Based on these findings the electrodes are explored for the photocatalytic degradation of methylene blue dye and are found to have significant efficiency upon LED and sunlight irradiation.

Comparative Analysis of Reactivity of Al and Ga Doped Garnet Solid State Electrolyte at the Interface with Li Metal

Comparative Analysis of Reactivity of Al and Ga Doped Garnet Solid State Electrolyte at the Interface with Li Metal

Improving the Cycle Stability of LiNiO2 through Al3+ Doping and LiAlO2 Coating.

In this study, we addressed the poor cycling and rate performance of LiNiO2, a material with ultrahigh nickel content considered a strong contender for high-energy-density lithium-ion battery cathodes. We introduced nano-Al2O3 during the lithiation process to achieve dual modified material through bulk phase element doping and in situ LiAlO2 coating. Comparison revealed notable improvements in the modified materials. In particular, LiNi0.99Al0.01O2 maintained a capacity retention rate of 73.1% after 300 cycles in a long-cycle test at 0.5C current density, outperforming the undoped material. In rate performance tests, the doped samples consistently exhibited higher discharge-specific capacities than that of the undoped counterpart. Notably, at a high current density of 5C, LiNi0.99Al0.01O2 exhibited a discharge-specific capacity of 101.75 mAh g-1. The results indicate that an appropriate amount of Al doping can effectively stabilize the layered structure of the cathode material and delay the irreversible phase transition from H2 to H3. Further, Al doping facilitates the formation of a LiAlO2 coating on the surface of the particles. This coating acts as a fast-ion conductor, enhancing the transport of lithium ions and reducing the erosion of the active material by the electrolyte.

Low-dose neutron irradiation effects on the elastoplastic deformation mechanisms of aluminum-doped gallium nitride under contact loading

The elastoplastic deformation mechanisms of irradiated aluminum (Al)-doped gallium nitride (GaN) under contact loading are investigated in this work using the nanoindentation simulations, which is of great significance for understanding the mechanical properties of the Al-doped GaN and guiding the design of durable and high-performance GaN-based devices. The mechanical behaviors of the Al-doped GaN with different doping concentrations are analyzed, including the indentation hardness, Young's modulus, elastic recovery rates, phase transformations, and stress distribution. It is found that Al doping increases their hardness, Young's modulus, and elastic recovery rates, and leads to an enlargement of the phase transformation regions, which is dominated by the high coordination number (CN) phase transformations. Furthermore, the effects of low-dose neutron irradiation on their elastoplastic deformation mechanisms are studied by triggering cascade collisions within the structure. When subjected to such irradiation, structural changes occur in the Al-doped GaN, their indentation hardness, Young's modulus, and elastic recovery rates increase remarkably, and its phase transformation mechanism is changed remarkably. The dislocation behaviors of the doped and undoped GaN are different under neutron irradiation. This study is important for capturing the mechanical stability and integrity of Al-doped GaN in an irradiation environment, as well as developing GaN-based devices with superior irradiation resistance.

Aluminum's role in tailoring the characteristics of room temperature co-sputtered gadolinium and aluminum-doped ZnO thin films

This study investigated the characteristics of gadolinium (Gd) and aluminum (Al) co-doped ZnO synthesized by co-sputtering at varying concentrations of Al. FESEM images revealed a morphology containing spherical-hexagonal nanostructures of different sizes based on the amount of Al. The EDS spectra clearly demonstrated the presence of Al, Gd, Zn, and O, confirming the successful incorporation of Gd and Al ions into the ZnO lattice in agreement with XRD profiles, not detecting any secondary phases. The photoluminescence study revealed that doping-induced defect states (oxygen vacancies, zinc vacancies, and zinc interstitial) were responsible for the many characteristic peaks of deep level emission observed in the photoluminescence spectra. Higher Al doping induced changes in magnetic characteristics as reflected in the greater root mean square value (δfrms), and the root mean square phase shift value (Φrms) in MFM analysis, whereas the magnetic correlation length (L) decreases. The incorporation of Al at higher concentrations into Gd-doped ZnO resulted in improved magnetic behavior suggesting the exchange interaction between Gd and Al ions mediated by oxygen vacancies. These results confirm that sufficient Al doping can efficiently improve the properties and magnetic behavior of ZnO-based DMS systems, which could potentially pave the way towards the realization of spin and/or optical based electronic devices.

Tailoring the Li+ Intercalation Energy of Carbon Nanocage Anodes Via Atomic Al-Doping for High-Performance Lithium-Ion Batteries.

Graphitic carbon materials are widely used in lithium-ion batteries (LIBs) due to their stability and high conductivity. However, graphite anodes have low specific capacity and degrade over time, limiting their application. To meet advanced energy storage needs, high-performance graphitic carbon materials are required. Enhancing the electrochemical performance of carbon materials can be achieved through boron and nitrogen doping and incorporating 3D structures such as carbon nanocages (CNCs). In this study, aluminum (Al) is introduced into CNC lattices via chemical vapor deposition (CVD). The hollow structure of CNCs enables fast electrolyte penetration. Density functional theory (DFT) calculations show that Al doping lowers the intercalation energy of Li+. The Al-boron (B)-nitrogen (N-doped CNC (AlBN-CNC) anode demonstrates an ultrahigh rate capacity (≈300 mAhg-1 at 10 Ag-1) and a prolonged fast-charging lifespan (862.82 mAhg-1 at 5 Ag-1 after 1000 cycles), surpassing the N-doped or BN-doped CNCs. Al doping improves charging kinetics and structural stability. Surprisingly, AlBN-CNCs exhibit increased capacity upon cycling due to enlarged graphitic interlayer spacing. Characterization of graphitic nanostructures confirms that Al doping effectively tailors and enhances their electrochemical properties, providing a new strategy for high-capacity, fast-charging graphitic carbon anode materials for next-generation LIBs.

Preparation and mechanical properties of Al-doped TiC films

Abstract Al-doped TiAlxC films were prepared on different substrates (single crystal Al2O3 (0001), stainless steel, and silicon wafer substrates) by co-sputtering, and microstructures and corresponding mechanical properties of TiAlxC films were tested and analyzed. The results indicate that the microhardness of the prepared TiAlxC films would decrease with the increased doping amount of Al while the corresponding friction coefficient would increase. With the increase of Al doping, the excess Al hinders the growth of the nanocrystalline phase in the TiAlxC film, thereby affecting the hardness and wear resistance of the TiAlxC film. When the Al doping is 4.1 at%, the hardness of the film reaches 2, 890 HV, while the friction coefficient is 0.2, indicating that a small amount of Al plays a role in solution strengthening the film. Therefore, the mechanical properties of the Al-doped TiAlxC films could be tailored by the doping amount of Al.

A Comparative Study of Congo Red Textile Dye Photodegradation Using ZnO Al and ZnO Al+Mn Nanoparticles

Photodegradation of Congo Red textile dye was successfully carried out using ZnO Al and ZnO Al+Mn nanoparticles synthesized using the bottom-up coprecipitation method. Powder X-ray diffraction provides information that Al and Mn doping successfully inserted in the host crystal structure while maintaining the Hexagonal Wurtzite crystal structure. However, a shift in the diffraction peak caused by the lattice distance changes with the addition of doping. FE-SEM EDS provides information that both nanoparticles are nonuniform sphere-like due to the addition of dopping, and each dopping is detected through EDS spectra. There is a decrease in the gap energy in each sample. ZnO Al nanoparticles have a gap energy of 3.29 eV, and ZnO Al+Mn nanoparticles have a gap energy of 3.28 eV. However, the decrease in the gap energy is not directly related to the percentage and kinetic rate of Congo Red photodegradation. Adding 5 mg of ZnO Al Nanoparticles powder could degrade Congo Red up to 97.9 % within 120 min using UV A radiation or 0.03504/min. At the same time, adding ZnO Al+Mn Nanoparticles powder with the same parameters could only degrade 67.6 % or 0.00759/min. HIGHLIGHTS Energy Bandgap Modification of ZnO Nanoparticles The incorporation of Al single dopants and Al, Mn co-dopants into ZnO nanoparticles synthesized via a bottom-up coprecipitation method significantly alters the energy bandgap. Al single doping resulted in a bandgap of 3.29 eV, while Al, Mn double doping yielded a bandgap of 3.28 eV. Enhanced Photocatalytic Activity of Al-Doped ZnO Al-doped ZnO nanoparticles exhibited superior photocatalytic activity toward the degradation of Congo Red textile dye. With a photodegradation rate constant of 0.03504 min⁻¹, these nanoparticles achieved 97.9 % degradation of Congo Red within 120 minutes. Comparative Photocatalytic Performance of Al, Mn Co-Doped ZnO While Al, Mn co-doped ZnO nanoparticles were synthesized using the same method, their photocatalytic performance for Congo Red degradation was notably lower than that of Al-doped ZnO. The calculated photodegradation rate constant was 0.00759 min⁻¹, resulting in 67.6 % degradation within the same timeframe. GRAPHICAL ABSTRACT

Study on the regulation mechanism of Al doping on the controllable photocatalytic performance of the ZnO@MgAl-LDH nanocomposite

The ZnO hollow nanospheres were initially prepared using the template method. Subsequently, MgAl-LDH nanosheets were in-situ grown on the surface of the nanospheres via the hydrothermal method, resulting in the synthesis of a type-I heterojunction-based ZnO@MgAl-LDH composite photocatalyst. However, the introduction of Al dopant into the ZnO hollow nanosphere component resulted in an elevation of the Fermi level of ZnO, which led to a change in the heterojunction type in the ZnO@MgAl-LDH composite from type-I to type-II. Consequently, the separation of photo-generated carriers in the Al-doped ZnO@MgAl-LDH composite was significantly enhanced, thereby improving its photocatalytic performance. Moreover, the mass ratio of Al-doped ZnO hollow nanospheres and MgAl-LDH was examined in greater detail to ascertain its influence on the photocatalytic performance of the composite photocatalyst. All Al-doped ZnO@MgAl-LDH composite samples exhibited enhanced photocatalytic performance in comparison to the composite sample without Al doping. Furthermore, when the mass of Al-doped ZnO hollow nanospheres was maintained at 0.100 g and the Mg2+ concentration in the precursor was 0.006530 mol/L, the resulting Al-doped ZnO@MgAl-LDH composite sample demonstrated the most optimal photocatalytic performance among all the investigated samples.

Optimization of Co4Sb11.5Te0.5 thermoelectric performance through Al filling under high temperature and high pressure

So far, the method of optimizing the thermoelectric properties of skutterudite CoSb3 is usually to achieve a breakthrough in high-properties thermoelectric merit by selecting excellent doping atoms and determining a reasonable percentage of atoms. In this study, we achieved the preparation of small atomic radius Al-filled Co4Sb11.5Te0.5 compounds by high-temperature and high-pressure (HTHP) synthesis methods. The thermoelectric properties of the samples AlxCo4Sb11.5Te0.5 were optimized from two dimensions: synthesis pressures (1.0 GPa, 1.5 GPa, 2.0 GPa) and Al filling concentration (x = 0.1, 0.2, 0.3, 0.5), ultimately achieving effective decoupling of electron-phonon transport properties. The experimental results show that Al doping can optimize the electrical transport properties of materials effectively, rapid synthesis method of HTHP can introduce abundant grain boundaries, diversification of grain sizes, a large number of dislocations and widely distributed nano second phase, etc. These microstructures in bulk materials form a multi-scale phonon scattering network in situ, which can effectively scatter phonons and reduce the lattice thermal conductivity effectively. After optimizing the synthesis pressure and Al filling concentration through orthogonal transformation, the sample Al0.3Co4Sb11.5Te0.5 prepared at a synthesis pressure of 1.5 GPa obtained a minimum lattice thermal conductivity value of 0.88 W m−1 K−1, a maximum power factor of 40.96 μ W cm−1 K−2 and a maximum zT value of 1.18 at 773.15 K.

Al concentration-dependent electrical modulation of Al-doped ZnO thin film using atomic layer deposition

A series of 150-nm-thick Al-doped ZnO (AZO) thin films with various Al doping concentrations were deposited by atomic layer deposition technique to determine their applicability in transparent electronic devices. For incorporation into transparent electrodes, the electrical properties of AZO films must be modulated to minimize the parasitic effect. The results show that AZO thin films with various Al dopant concentrations had different work-functions and electrical contact properties, while the other physical characteristics were not significantly changed. Hence, AZO thin films can be used as transparent conducting oxide materials and are potential alternatives for the currently used indium-tin-oxide (ITO) thin films.

Multiband MgAl0.05Ge0.95O3:0.3%Pr3+ Persistent Phosphor as Efficient Tracers in Crude Oil Emulsions.

The use of fluorescent nanoparticles (NPs) for tracing purposes in oilfields encounters challenges due to background interferences under constant external excitation caused by organic residues present in crude oil. This results in insufficient sensitivity and lower tracer detection limits in the crude oil/water emulsions. In this study, we present the synthesis of persistent luminescent NPs, showcasing their remarkable application as tracers in crude oil. The multiband MgAl0.05Ge0.95O3:0.3%Pr3+ persistent NPs were synthesized via the sol-gel method. Through meticulous experimentation and analysis, our study unveils a novel avenue for efficient and lasting traceability in crude oil. The synthesized NPs emit light across the visible, near-infrared, and shortwave infrared regions, allowing for versatile detection. The unique luminescent properties of these NPs, particularly their ability to persist in emitting light without a continuous external excitation, enable their effective use as tracers in crude oil/water emulsions where background fluorescence typically poses a significant challenge. By employing these persistent NPs in background fluorescence-free conditions, we achieve ultrahigh sensitivity in detecting these NPs in crude oil. Our research reveals that the doping of Al3+ ions significantly enhances both the afterglow intensity of MgGeO3:0.3%Pr3+ phosphor and the afterglow decay time of Pr3+ emission. This characteristic enables the re-excitation of MgAl0.05G0.95O:0.3%Pr3+ NPs within the emulsion, allowing for repeated spectral and imaging acquisition. This high sensitivity not only facilitates precise imaging of NPs in crude oil but also enables long-term monitoring in real-time, offering valuable insights for oilfield operations.

Efficient recovery of lithium from shale gas wastewater: Fe, Ni, and Al doping of H1.33Mn1.67O4 for improved adsorption capacity and manganese loss reduction

To minimize manganese loss during acid leaching and to enhance the lithium adsorption capacity from shale gas wastewater of H1.33Mn1.67O4, this adsorbent material was doped with metallic elements in this study. Doping was achieved using solid-phase synthesis, resulting first in a Li1.33RXMn1.67−XO4 (R = Fe, Ni, Al) precursor powder through high-temperature calcination. Then, lithium was leached out under acidic environment to obtain the desired H1.33RXMn1.67−XO4 (HMO-R) adsorbents. The equilibrium adsorption capacities of HMO-R powders were measured as 20.7 mg/g, 20.7 mg/g, and 29.0 mg/g, for Fe, Ni, and Al dopants, respectively, surpassing that of the former H1.33Mn1.67O4 (13.7 mg/L). Moreover, an average reduction of manganese loss by 30% for HMO-R was observed during lithium recovery/extraction cycles by acid leaching compared to undoped Li1.33Mn1.67O4. Overall, the doped adsorbent exhibited a stable crystal structure and high adsorption capacity, enhanced stability, performance, and efficiency in cycling experiments with respect to the undoped material.